Azithromycin is a type of antibiotic used to treat a wide range of bacterial infections. It is commonly prescribed for infections affecting the tonsils, sinusitis, ears, nose, throat, skin, soft tissues, and lungs (such as pneumonia). Azithromycin works by inhibiting the production of essential proteins that bacteria need to survive and function. This action halts bacterial growth and helps prevent the infection from spreading. The U.S. FDA approved azithromycin for medical use in 1991.
BRAND NAMES:
Zithromax - Zithromax is available as film coated oral capsules containing azithromycin as the main active ingredient with composition 250 & 500 mg.
Azasite – Azasite is an ophthalmic solution, azithromycin is the main active ingredient available with composition 2.5ml of 1% sterile topical ophthalmic solution.
MECHANISM OF ACTION:
Azithromycin binds to the 23S rRNA of the bacterial 50S ribosomal subunit, blocking protein synthesis by preventing the passage of aminoacyl-tRNA and the elongating peptide chain through the ribosome. Compared to erythromycin, azithromycin has a stronger binding affinity to ribosomes in Gram-negative bacteria, which may contribute to its enhanced effectiveness against these pathogens.After administration, azithromycin rapidly exits the bloodstream and accumulates in tissues. It easily penetrates cell membranes, making it particularly effective against intracellular organisms. In certain non-bacterial organisms, azithromycin targets the 50S ribosome within the apicoplast—an endosymbiosis-derived organelle that resembles bacterial protein synthesis systems and is essential for parasite metabolism.
PHARMACOKINETICS:
Absorption: A 250 mg dose of azithromycin has an absolute bioavailability of around 38%. When given as an oral suspension with food, the peak plasma concentration increases by 56%, although the overall drug exposure (AUC) remains the same.
Distribution: Azithromycin shows strong tissue penetration and accumulates well within cellsAzithromycin’s binding to serum proteins is concentration-dependent, decreasing from 51% at a concentration of 0.02 µg/mL to 7% at 2 µg/mL.
Metabolism: Azithromycin is mainly metabolized in the liver. Following a single 500 mg oral or intravenous dose, its plasma concentration declines in multiple phases, resulting in an average terminal half-life of approximately 68 hours.
Excretion: Azithromycin is primarily eliminated unchanged through bile excretion.
PHARMACODYNAMICS:
Azithromycin is a macrolide antibiotic that exhibits broad-spectrum activity, especially effective against Gram-positive bacteria, certain Gram-negative bacteria, and atypical pathogens. Its pharmacodynamic effects are primarily based on inhibition of bacterial protein synthesis, leading to a bacteriostatic action, though it can be bactericidal at high concentrations or against highly susceptible organisms.
DOSAGE AND ADMINISTRATION:
Azithromycin is available in several oral forms, such as tablets (250 mg and 500 mg), single-dose packets (1 gram to be mixed with ¼ cup or 60 mL of water), and reconstitutable suspensions (100 mg/5 mL and 200 mg/5 mL). All of these formulations can be taken with or without food. It should be administered as an intravenous infusion lasting at least 60 minutes and must not be given via intramuscular injection or IV bolus. Additionally, a 1% azithromycin ophthalmic solution is available in a 2.5 mL bottle for treating bacterial conjunctivitis. The extended-release oral formulation of azithromycin is no longer available.
Adult dosage:
The typical adult dose of azithromycin is 250 mg or 500 mg once daily for 3 to 5 days, depending on the severity of the infection. In some cases, such as chlamydia infection, a single oral dose of 1 gram may be recommended.
Acute Otitis Media (≥6 months old):
- Single dose of 30 mg/kg,
- 10 mg/kg once daily for a period of 3 days
- 10 mg/kg on the first day, followed by 5 mg/kg daily for the next 4 days
Community-Acquired Pneumonia (≥6 months old):
- 10 mg/kg taken orally on Day 1, then 5 mg/kg once daily for the subsequent 4 days.
Acute Bacterial Sinusitis:
- 12 mg/kg once daily for 5 days, with a maximum dose of 500 mg per day.
- Pharyngitis/Tonsillitis (≥2 years old):
- 12 mg/kg once daily for 5 days, with a maximum daily dose of 500 mg.
DRUG INTERACTIONS:
Before taking azithromycin it is required to discuss with doctor, if the patient is undergoing treatment for any other health issues. It is because, some drugs can be interact with azithromycin and can lead to adverse effects. The following drugs should be avoided while taking azithromycin. Migraine - Ergotamine
- Heart failure - Digoxin
- Gout medications - Colchicine
- Anticoagulants – Warfarin
- Immunosuppressants – Cyclosporin
- Antihistaines – Terfenadine
- HIV medicine -Nelfinavir, Zidovudine, Rifabutin
- Asthma Medicine- Theophylline
- Malaria medicines – Hydroxychloroquine, chloroquine.
CONTRAINDICATIONS:
Azithromycin is contraindicated in patients with hypersensitive to its components.
ADVERSE EFFECTS:
- Stomach cramps
- Dizziness
- Diarrhea
- Headache
- Vomting
- Itching & swelling at injection site
OVERDOSE:
Taking overdose of azithromycin can lead to some toxic effects like
- Rashes
- Fever
- Cardiac Arrhythmia
